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Beneficial Use of Graywater and Stormwater: An Assessment of Risks, Costs, and Benefits

Completed

Chronic and episodic water shortages are becoming common in many regions of the United States, and population growth in water-scarce regions further compounds the challenges.. This report analyzes the risks, costs, and benefits on various uses of graywater and stormwater, examining the technical, economic, regulatory, and social issues associated with graywater and stormwater capture for a range of uses, including non-potable urban uses, irrigation, and groundwater recharge. It considers the quality and suitability of water for reuse, treatment and storage technologies, and human health and environmental risks of water reuse.

Description

An ad hoc committee will conduct a study and prepare a report that will analyze the risks, costs, and benefits of various beneficial uses of stormwater and graywater and approaches needed for its safe use. The study will address:

  1. Quantity and suitability. How much stormwater capture and graywater reuse occurs in the United States and for what applications? What is the suitability--in terms of water quality and quantity--of captured stormwater and graywater for various purposes considering available treatment options? What is the realistic potential to significantly increase stormwater and graywater use in the United States, and where regionally would increases in these practices have the most benefit? How would significant increases in the beneficial use of stormwater and graywater affect water demand, downstream water availability, aquifer recharge, and ecological stream flows? What research should be pursued to understand these issues adequately?
  2. Treatment and storage. What are typical levels and methods of treatment and storage for stormwater capture and graywater reuse for various end uses? What types of treatment are available to address contaminants, odors, and pathogens, and how do these treatment methods compare in terms of cost and energy use? What research opportunities should be pursued to produce improved technologies and delivery and ensure adequate safeguards to protect public health and the environment?
  3. Risks. What are the human health and environmental risks of using captured stormwater and graywater for various purposes? What existing state and regulatory frameworks address the beneficial use of stormwater and graywater, and how effective are they in assuring the safety and reliability of these practices? What lessons can be learned from experiences using captured stormwater and graywater both within and outside the United States that shed light on appropriate uses with varying levels of treatment? What upstream (i.e., household-level) actions can reduce risks?
  4. Costs and benefits. What are the costs and benefits of the beneficial use of stormwater and graywater (including nonmonetized costs and benefits, such as effects on water and energy conservation, environmental impacts, and on wastewater infrastructure)? How do the economic costs and benefits generally compare with other supply alternatives? Can cost improvements be achieved through research?
  5. Implementation. What are the legal and regulatory constraints on the use of captured stormwater and graywater? What are the policy implications regarding the potential increased use of stormwater and graywater as significant alternative sources of water for human consumption and use?

As part of its review, and to help benchmark U.S. standing worldwide, the committee will consider international experiences in stormwater and graywater management, as it deems relevant.

Contributors

Committee

Chair

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Sponsors

City of Madison, Wisconsin

EPA

National Academy of Sciences Arthur L. Day Fund

National Academy of Sciences Cecil and Ida Green Fund

National Academy of Sciences George and Cynthia Mitchell Endowment for Sustainability Science

National Academy of Sciences W.K. Kellogg

National Science Foundation

National Water Research Institute

The Los Angeles Department of Water and Power

Water Environment Research Foundation

WateReuse Research Foundation

Staff

Stephanie Johnson

Lead

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